The present invention relates to recovery of solvents from the effluent which evolves in a vacuum drying operation, and refers more particularly to a cold trap unit wherein condensing of the solvents is effected.
In the drying of, e.g., solvent-containing biological specimens, the drying of specimens commonly is done in a chamber maintained under a condition of vacuum. During drying, an effluent in which vaporized solvents are contained is given off from the operation. It is understood that the solvents should be recovered from the effluent for several reasons.
One is the need to reduce as much as possible carryover of solvent from the chamber to the vacuum pump used to maintain the chamber under vacuum as the solvents have corrosive properties that can cause pump damage. Another reason is to minimize entry of solvents to normal ambient atmosphere since solvents presence in the atmosphere can be harmful to humans.
The common practice for solvents recovery utilized two separate cold traps. Effluent from the chamber is directed into a first of these cold traps after the effluent leaves the drying chamber but before the location of the inlet to the vacuum pump. Solvents in the effluent condense is this first cold trap but solvent condensation therein may not be total so that the effluent outflowing the first cold trap to the inlet of the vacuum pump contains solvents carryover.
This solvents carryover passes through the vacuum pump and leaves is as gas exhaust from the pump outlet. The gas exhaust is then directed through a second cold trap to condense out the carryover solvents.
The foregoing described recovery practice has some disadvantages. Notable is the need for space for locating two separate cold traps. Space sometimes is at a premium in a laboratory where many of such practiced drying operations take place so that finding locations for two cold traps proximal the drying chamber and convenient to the scientist or technician can be a problem.
Since cold traps operate at sub-zero temperatures, it is necessary to provide a separate refrigeration source for each of the two cold traps. Additionally, use of separate cold traps does not allow convenience of immediate presence at a single location of all collected condensate thereby to facilitate disposal of same.